The overall vision of our NIGMS-supported program is to address the molecular mechanisms of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) signal transmission as guided by scaffold proteins. Essential for the normal functioning of the cell, the ERK1/2 ability to ?rewire? signaling pathways is a major problem for clinical intervention. The rationale for the proposed studies is that a thorough understanding of the mechanism by which key regulators, such as scaffold protein Shoc2, modify ERK1/2 signaling is essential for understanding dysregulated mechanisms in ERK1/2-related diseases and for identifying new drug targets. Our studies have raised many exciting questions, and the most transformative research will be pursued in the next five-year period. Our efforts during the first cycle of NIGMS funding led to the discovery that the ubiquitin machinery regulates the signal transmission of ERK1/2 signals through the Shoc2 scaffolding module and controls assembly of the proteins in the complex. We identified key enzymes modulating the ability of Shoc2 to transmit ERK1/2 signals. We then discovered that organized spatial distribution of the Shoc2 complexes is critical for the proper transmission of ERK1/2 signals. Our work further revealed a distinct function of the signals transduced by the Shoc2 scaffold in ERK1/2 in mediating cell adhesion and motility. We also established that loss of Shoc2 in zebrafish has a systemic effect of on early development recapitulating congenital malformations observed in patients with Shoc2 mutations. For MIRA application, we propose to define the mechanisms by which endosomal sorting regulates the ubiquitin-driven remodeling of the Shoc2 complexes and signaling. The key steps that segregate Shoc2 into the distinct intracellular sorting pathways will be delineated. The molecular details of how Shoc2-activated ERK1/2 signals promote early developmental stages will be determined. We will use an innovative comprehensive approach encompassing genetic, state-of-the-art microscopy, as well as cell-based and biophysical methodologies. Of note, we will use zebrafish as a vertebrate model to investigate the in vivo effect of Shoc2 gene editing on the early stages of development since they offer distinct advantages for studies of development, including their transparency, as well as external and rapid development. The proposed research is expected to produce an ambitious and comprehensive mechanistic understanding of how Shoc2 is involved in determining the specificity of ERK1/2 signaling outcomes, and has the potential for high impact by laying the groundwork for future studies on developmental disorders and contributing to the advancement of novel therapeutic strategies and biomarkers.